JP2017519843A - Terbium molybdate doped with europium or samarium - Google Patents

Abstract

The present invention relates to terbium molybdate doped with europium or samarium, to the process for the preparation of said compounds and to the use of the claimed terbium molybdate doped with europium or samarium as a conversion phosphor. The present invention also relates to a light emitting device comprising the claimed europium or samarium doped terbium molybdate.

Description

  The present invention relates to terbium molybdate doped with europium or samarium, methods for the preparation of these compounds and the use of terbium molybdate doped with europium or samarium according to the invention as conversion phosphors. The invention further relates to a light emitting device comprising terbium molybdate doped with europium or samarium according to the invention.

Inorganic fluorescent powders that can be excited in the blue and / or UV spectral region are mainly important as conversion phosphors for phosphor-converted LEDs, or pc-LEDs for short. On the other hand, many conversion phosphor systems are known, such as alkaline earth metal orthosilicates, thiogallates, garnets, nitrides and oxynitrides, each of which is doped with Ce ³⁺ or Eu ²⁺ . In addition to yellow or green emitting garnet or orthosilicate, to achieve a warm white light source with a color temperature of <4000K based on blue or UV-A emitting (In, Ga) N LEDs, primary radiation (370 There is a need for a red-emitting phosphor having an emission wavelength longer than 600 nm that emits sufficiently strongly at the corresponding wavelength (˜480 nm). At the same time, the stability of these phosphors must be as high as that of garnet or orthosilicate so that no undesired color point migration occurs during the lifetime of the solid state light source.

Many phosphors that meet these requirements have been proposed or developed for this purpose in the last 20 years. The phosphors used to date, namely (Ca, Sr) S: Eu, (Ca, Sr) AlSiN ₃ : Eu and (Ca, Sr, Ba) ₂ Si ₅ N ₈ : Eu, are all active Eu ²⁺ It is distinguished by both a broad absorption spectrum and also a broad emission band. The main drawback of these Eu ²⁺ activation materials is their relatively high sensitivity to photodisintegration, since divalent Eu ²⁺ has a tendency to photoionization, especially in host materials with a relatively small band gap. .

A further disadvantage is the fairly high half-width of the Eu ²⁺ emission band, which is evident from a moderate lumen equivalent (<200 lm / W) when the color point is in the deep red spectral region. This observation applies particularly to the phosphors (Ca, Sr) S: Eu and (Ca, Sr) AlSiN ₃ : Eu.

It is therefore desirable to develop a red-emitting phosphor that does not have these drawbacks. Thus, one of the objects of the present invention is to provide this type of phosphor.
Surprisingly, the inventors have found that terbium molybdate doped with europium or samarium fulfills the aforementioned requirements.

CN 103275713 A includes in this connection the general formula R ^III _{2 (1-x)} Eu _2x Mo ₄ O ₁₅
^{Wherein, R III} is an element ^{La 3+, Ce 3+, Pr 3+} , Nd 3+, Sm 3+, Gd 3+, Tb 3+, Dy 3+, Ho 3+, Er 3+, Tm 3+, Yb 3+, Lu 3+, Sc 3+ and Selected from Y ³⁺ and 0.0001 ≦ x <1.0.
The compound represented by these is disclosed. However, terbium molybdate according to the present invention is not disclosed here. As is further known to those skilled in the art, Tb ⁴⁺ is also produced simultaneously with Tb ^{3+ in} the preparation of the compound represented by the foregoing formula, and a broad absorption band is produced by the corresponding Tb ⁴⁺ fraction in the compound, It undesirably spreads in the red light region, thereby significantly impairing the phosphor properties of the corresponding compound.

The present invention is therefore of the formula I
_{(Tb 2) x (Mo 1} -b W b) y O 3x + 3y: Ln I
In which Ln represents Sm ³⁺ or Eu ³⁺ ;
x represents 1, 2 or 3; 1 ≦ y ≦ 8; and 0 ≦ b <1;
y preferably corresponds to an integer multiple of 1-8,
It is related with the compound represented by these.

  The compounds according to the invention can usually be excited in the blue spectral region, preferably about 370 to 480 nm, and usually have a red line emission in the red spectral region at about 615 or 660 nm.

  In the context of this application, blue light indicates light with an emission maximum of 400-459 nm, cyan light indicates light with an emission maximum of 460-505 nm, and green light has light with an emission maximum of 506-545 nm. Yellow light represents light having an emission maximum of 546 to 565 nm, orange light represents light having an emission maximum of 566 to 600 nm, and red light represents light having an emission maximum of 601 to 700 nm. The compound according to the present invention is preferably a red emission conversion phosphor.

Furthermore, the compounds according to the invention are distinguished by a high photoluminescence quantum yield of more than 80%, preferably more than 90%, particularly preferably more than 95%.
Photoluminescence quantum yield (also referred to as quantum yield or quantum efficiency) describes the ratio between the number of photons emitted and absorbed by a compound.
Furthermore, the phosphor according to the invention has a high value for lumen equivalent (≧ 250 lm / W) and is distinguished by a higher chemical and photochemical stability.

In a preferred embodiment, the compound of formula I is selected from formula Ia.
_{(Tb 2-a Ln a)} x (Mo 1-b W b) y O 3x + 3y Ia
Where Ln and b have one of the meanings given under formula I,
x = 1;
1 ≦ y ≦ 3; and 0.1 ≦ a ≦ 1.

The compounds according to the invention are distinguished by absorption intensities at 395 nm, 465 nm and 487 nm, which are relatively high, especially for phosphors doped with Ln. Absorption band the last-mentioned is due to the presence of trivalent _{^{Tb 3+ (7 F 6 - 5}} D 4), "green" ^{Tb 3+} luminescence, to Ln at a concentration 0.2 ≦ a ≦ 1 It is virtually completely quenched by efficient energy transfer.

In a preferred embodiment of the invention, Ln is equal to Eu ³⁺ . Preference is therefore given to formulas I or Ia, where 0.1 <a ≦ 1, particularly preferably 0.2 ≦ a ≦ 1, in particular 0.4 <a ≦ 1 is a compound.
In a further preferred embodiment, Ln in the compounds of the formulas I and Ia according to the invention is equal to Sm ³⁺ , preferably 0.1 ≦ a ≦ 1, particularly preferably 0.2 <a ≦ 1, and further 0.4 ≦ a ≦ 1.

In accordance with the present invention, the emission maximum of a compound represented by Formulas I and Ia, where Ln is equal to Eu ³⁺ or Sm ³⁺ is also optionally incorporated into the yellow spectral region by doping into a smaller amount of Ln. Particular preference is given here to compounds in which 0 <a <0.1, preferably 0 <a ≦ 0.05, particularly preferably 0 <a ≦ 0.01.

  In a further embodiment, hexavalent molybdenum in the compounds of formulas I and Ia can be partially replaced by hexavalent tungsten (b> 0). Preference is given here to compounds in which 0 ≦ b <0.8, particularly preferably 0 ≦ b <0.5, in particular 0 ≦ b <0.3. Particularly preferred, however, are compounds of the formulas I and Ia, in which b is equal to 0.

  Particular preference is given to compounds of the formulas I and Ia, in which x is equal to 1 and y is simultaneously equal to 3, further represented by formulas I and Ia, in which x is equal to 2 and y is simultaneously equal to 7. And the compounds of formulas I and Ia, where x is equal to 3 and y is simultaneously equal to 8.

In particular, the compounds represented by the following dependent formula (Tb _1-a Eu _a ) ₂ Mo ₃ O _{12 according} to the present invention are distinguished by the presence of a mixed crystal series without gaps.
A mixed crystal refers to a crystal composed of at least two different chemical elements, where the corresponding atoms or ions are distributed randomly.

The compounds according to the invention are particularly preferably selected from the following dependent formulas:
Here, the compounds of the formulas I and Ia are preferably in phase-pure form.

  The phase purity of the crystalline powder can be investigated by an X-ray diffraction pattern (ie, whether the sample consists of only one crystalline compound (phase pure) or multiple compounds (multiphase)). In phase pure powder, all reflections can be observed and assigned to compounds.

  The invention further relates to a process for the preparation of the compounds according to the invention, wherein in step a) a suitable starting material selected from nitrides and oxides or corresponding reactive forms is mixed, and in step b) the mixture The method is characterized in that it is thermally treated.

The process is preferably characterized by the following process steps:
(A) preparation of a mixture comprising a europium or samarium source, a molybdenum source and a terbium source, and optionally also a tungsten source;
(B) Calcination of the mixture under oxidizing conditions.

The europium or samarium source used in step (a) can be any possible europium or samarium compound capable of producing terbium molybdate doped with europium or samarium. The europium or samarium source used is preferably an oxide or nitride of the element, in particular europium oxide (especially Eu ₂ O ₃ ) and / or europium nitride (EuN) and also especially samarium oxide (especially Sm ₂ O _3). ) And / or samarium nitride (SmN), in particular Eu ₂ O ₃ or Sm ₂ O ₃ .

  The terbium source used in step (a) can be any possible terbium compound capable of producing europium-doped terbium molybdate. The terbium source used in the process according to the invention is preferably terbium nitride and / or terbium oxide.

  The molybdenum and / or tungsten source used in step (a) can be any possible molybdenum and / or tungsten compound capable of producing terbium molybdate according to the present invention. The molybdenum and / or tungsten source used in the process according to the invention is preferably the corresponding nitride and / or oxide.

  The compounds are preferably used in a ratio relative to each other such that the number of atoms of the corresponding element Ln, molybdenum and / or tungsten and terbium essentially corresponds to the desired ratio in the product represented by the above formula . In particular, the theoretical mixing ratio is used here.

  The starting compounds in step (a) are preferably used in powder form and processed with each other, for example by means of a mortar, to obtain a homogeneous mixture. For this purpose, the starting compound can preferably be suspended in an inert organic solvent known to those skilled in the art, for example acetone. In this case, the mixture is dried before calcination.

The calcination in step (b) is performed under oxidizing conditions. Oxidation conditions are taken to mean any possible oxidizing atmosphere, for example air or other oxygen-containing atmosphere.
The calcination is preferably carried out at a temperature in the range from 700 ° C to 1200 ° C, particularly preferably from 800 ° C to 1000 ° C and especially from 850 ° C to 950 ° C. The calcination duration here is preferably 2 to 14 h, more preferably 4 to 12 h and especially 6 to 10 h.

Calcination is preferably performed by introducing the resulting mixture into a high temperature oven, such as a boron nitride container. The high temperature oven is a tubular oven including, for example, a molybdenum foil tray.
After calcination, the compound obtained can optionally be homogenized, where the corresponding grinding process can be carried out in a suitable solvent, for example wet in isopropanol or dry.

In a further embodiment, the compounds according to the invention can be coated. Suitable for this purpose are all coating methods known to the person skilled in the art according to the prior art and used for phosphors. Suitable materials for the coating are in particular metal oxides and metal nitrides, in particular alkaline earth metal oxides such as Al ₂ O ₃ and alkaline earth metal nitrides such as AlN and SiO ₂ . The coating can here take place, for example, by a fluidized bed process. Further suitable coating methods are known from JP 04-304290, WO 91/10715, WO 99/27033, US 2007/0298250, WO 2009/065480 and WO 2010/075908. It is also possible to apply organic coatings as an alternative to and / or in addition to the aforementioned inorganic coatings. The coating can have a beneficial effect on the stability and dispersibility of the compound.

  The invention further relates to the use of the compounds according to the invention as phosphors, in particular as conversion phosphors.

  The term “conversion phosphor” in the meaning of the present application absorbs radiation in one wavelength region of the electromagnetic spectrum, preferably in the blue or UV spectral region, preferably in the red or orange spectrum in another wavelength region of the electromagnetic spectrum. It is taken to mean a material that emits visible light in the region, in particular in the red spectral region. The term “radiation-induced luminescence effect” should also be understood in this context, ie the converted phosphor absorbs radiation in one wavelength region and emits radiation in another wavelength region with a certain efficiency. The term “shift in emission wavelength” is taken to mean that the converted phosphor emits light at various wavelengths, ie, shifted to a shorter or longer wavelength compared to another or similar converted phosphor. Is done. The emission maximum moves in this way.

  The invention further relates to a luminescence conversion material comprising one or more compounds represented by one of the aforementioned formulas according to the invention. The luminescence conversion material may consist of one of the compounds according to the invention and in this case will be equivalent to the term “converting phosphor” as defined above.

  It is also possible for the luminescence conversion material according to the invention to comprise further conversion phosphors in addition to the compounds according to the invention. In this case, the luminescence conversion material according to the invention comprises a mixture of at least two conversion phosphors, where one of these is a compound according to the invention. It is particularly preferred that the at least two conversion phosphors are phosphors that emit light of different wavelengths that are complementary to each other. Since the compounds according to the invention are red-emitting phosphors, this is preferably used in combination with green or yellow-emitting phosphors or also with cyan or blue-emitting phosphors.

  Alternatively, the red emission conversion phosphor according to the present invention can also be used in combination with (one) blue and green emission conversion phosphor (s). Alternatively, the red luminescence conversion phosphor according to the present invention can also be used in combination with (one) green luminescence conversion phosphor (s). Thus, it may be preferred to use the conversion phosphor according to the invention in combination with one or more further conversion phosphors in the luminescence conversion material according to the invention, whereby both preferably emit white light.

In general, any possible conversion phosphor can be used as a further conversion phosphor that can be used with the compounds according to the invention. Here, for example, the following are suitable:

  The compounds according to the invention give good LED properties even when used in small amounts. LED quality is here described by conventional parameters such as color rendering index, correlated color temperature, lumen equivalent or absolute lumen, or color points in CIE x and CIE y coordinates.

  Color rendering index or CRI is a dimensionless illumination quantity familiar to those skilled in the art, which compares the color reproduction fidelity of artificial light sources to that of sunlight or filament light sources (the latter two being 100 With CRI).

  CCT or correlated color temperature is an amount of illumination familiar to those skilled in the art having unit Kelvin. As the value increases, white light from the artificial radiation source appears cold to the viewer. CCT follows the concept of a black body radiator, and its color temperature describes a so-called Planck curve in the CIE chart.

  Lumen equivalent is an amount of illumination familiar to those skilled in the art having units of lm / W, describing the magnitude of the photometric luminous flux in the lumen of the light source at a certain radiometric radiant power having unit watts. As the lumen equivalent increases, the light source becomes more efficient.

  Lumen is a photometric illumination quantity familiar to those skilled in the art, which describes the luminous flux of the light source, which is the extent of the total visible rays emitted by the light source. As the luminous flux increases, the light source appears bright to the viewer.

  CIE x and CIE y represent coordinates in a standard CIE color chart (here standard observer 1931) familiar to those skilled in the art, thereby describing the color of the light source.

All the quantities mentioned above are calculated by methods well known to those skilled in the art from the emission spectrum of the light source.
In this connection, the invention further relates to the use of the compounds according to the invention or of the luminescence conversion materials according to the invention described above in light sources.

  The light source is particularly preferably an LED, in particular a phosphor-converted LED, abbreviated pc-LED. The luminescence conversion material comprises at least one further conversion phosphor in addition to the conversion phosphor according to the invention, in particular so that the light source emits white light or light having a certain color point (color on demand principle) Particularly preferred here. “Color on demand principle” is taken to mean the achievement of light having a certain color point in a pc-LED using one or more conversion phosphors.

The invention thus further relates to a light source comprising a primary light source and a luminescence conversion material.
Here too, it is particularly preferred that the luminescence conversion material comprises at least one further conversion phosphor in addition to the conversion phosphor according to the invention, so that the light source preferably emits white light or light having a certain color point.

  The light source according to the invention is preferably a pc-LED. A pc-LED generally includes a primary light source and a luminescence conversion material. The luminescence conversion material according to the invention is dispersed for this purpose in a resin (for example epoxy or silicone resin) or, if at a suitable size ratio, directly on the primary light source or alternatively depending on the application. Can then be remotely located (subsequent placement also includes “remote phosphor technology”).

  The primary light source is a semiconductor chip, a light emitting light source such as ZnO, so-called TCO (transparent conductive oxide), an arrangement based on ZnSe or SiC, an arrangement based on an organic light emitting layer (OLED) or a plasma or discharge source, most preferably Can be a semiconductor chip. When the primary light source is a semiconductor chip, it is preferably light emitting indium aluminum gallium nitride (InAlGaN) as is known from the prior art. Possible forms of primary light sources of this type are known to those skilled in the art. Furthermore, a laser is suitable as a light source.

  For use in light sources, in particular pc-LEDs, the luminescence conversion material according to the invention can also be converted into any desired profile, for example spherical particles, flakes and structured materials and ceramics. These shapes are summarized under the term “molded body”. The molded body is thus a luminescence conversion molded body.

  The invention further relates to a lighting unit comprising at least one light source according to the invention. This type of lighting unit is mainly used in display devices with back illumination, in particular liquid crystal display devices (LC displays). The invention therefore also relates to this type of display device.

  In the lighting unit according to the invention, the optical coupling between the luminescence conversion material and the primary light source (especially the semiconductor chip) is preferably caused by a photoconductive arrangement. In this way, it is possible that the primary light source is installed in a central position and for this purpose is optically coupled to the luminescence conversion material by a photoconductive device, for example an optical fiber.

  In this way, to achieve a lamp adapted to the desired lighting, consisting of one or more different conversion phosphors, which can be arranged to form a light screen and a light guide, coupled to a primary light source, Is possible. In this way, a powerful primary light source is placed in a location that is convenient for electrical installation, a lamp containing luminescence conversion material is installed, and it is simply guided to the light guide without the use of additional electrical wiring. It is possible to couple by placing the waveguide in any desired position.

  All variations of the invention described herein can be combined with each other as long as the respective aspects are not mutually exclusive. In particular, based on the teachings of this specification as part of routine optimization, the precise combination of the various variations described herein to obtain certain particularly preferred embodiments is an obvious operation. It is. The following examples illustrate the present invention and are specifically intended to illustrate the results of such exemplary combinations of the described inventive variations.

  However, they should not be considered limiting in any way and are instead intended to stimulate generalization. All compounds or components that can be used in the manufacture are known and are commercially available or can be synthesized by known methods. The temperature shown in the examples is always in ° C. Furthermore, it goes without saying that in both the description and also in the examples, the amount of component added in the composition is always added up to a total of 100%. Percent data should always be considered in a given context.

Example a) Tb _1.998 Eu _0.002 Mo ₃ O ₁₂
1.8684 g (2.498 mmol) Tb ₄ O ₇ , 2.1591 g (15.00 mmol) MoO ₃ and 0.0018 g (0.0050 mmol) Eu ₂ O ₃ were powdered with the aid of acetone in an agate mortar To. The powder is dried, transferred into a porcelain crucible and heated twice at 900 ° C. for 10 h in air.

b) Tb _1.8 Eu _0.2 Mo ₃ O ₁₂
1.6832 g (2.250 mmol) Tb ₄ O ₇ , 2.1591 g (15.00 mmol) MoO ₃ and 0.1760 g (0.5000 mmol) Eu ₂ O ₃ were powdered with the aid of acetone in an agate mortar To. The powder is dried, transferred into a porcelain crucible and heated twice at 900 ° C. for 10 h in air.

c) TbEuMo ₃ O ₁₂
0.9351 g (1.250 mmol) of Tb ₄ O ₇ , 2.1591 g (15.00 mmol) of MoO ₃ and 0.8800 g (2.500 mmol) of Eu ₂ O ₃ were powdered with the aid of acetone in an agate mortar. To. The powder is dried, transferred into a porcelain crucible and heated twice at 900 ° C. for 10 h in air.

d) Tb _1.8 Sm _0.2 Mo ₃ O ₁₂
1.6823 g (2.250 mmol) Tb ₄ O ₇ , 2.1591 g (15.00 mmol) MoO ₃ and 0.1744 g (0.500 mmol) Sm ₂ O ₃ were powdered with the aid of acetone in an agate mortar To. The powder is dried, transferred into a porcelain crucible and heated twice at 900 ° C. for 10 h in air.

e) Tb _1.2 Eu _0.8 Mo ₃ O ₁₂
1.1215 g (1.500 mmol) Tb ₄ O ₇ , 2.1591 g (15.00 mmol) MoO ₃ and 0.7038 g (2.000 mmol) Sm ₂ O ₃ were powdered with the aid of acetone in an agate mortar To. The powder is dried, transferred into a porcelain crucible and heated twice at 900 ° C. for 10 h in air.

f) Production of pc-LEDs using phosphors of composition Tb _1.2 Eu _0.8 Mo ₃ O ₁₂ produced according to the invention: Fluorescence with 2 g of composition Tb _1.2 Eu _0.8 Mo ₃ O ₁₂ The body is weighed out and mixed with 8 g of optically clear silicone and then mixed homogeneously in a revolving mixer so that the phosphor concentration in the overall object is 20% by weight. The silicone / phosphor mixture obtained in this way is applied to the chip of a near UV semiconductor LED with the aid of an automatic distributor and cured with the supply of heat. The near UV semiconductor LED used for LED characterization in this example has an emission wavelength of 395 nm and operates at a current strength of 350 mA. Photometric characterization of the LEDs is performed using an Instrument Systems CAS 140 spectrometer and an accompanying ISP 250 integrated sphere. The LED is characterized by determining the wavelength dependent spectral power density. The resulting spectrum of light emitted by the LED is used to calculate the color point coordinates CIE x and y.

FIG. 1 is an X-ray diffraction pattern of Tb _2-x Ln _x Mo ₃ O ₁₂ for Cu K-alpha rays. FIG. 2 is the reflection spectrum of Tb _1.999 Eu _0.001 Mo ₃ O ₁₂ for BaSO ₄ as a white standard. FIG. 3 shows the reflection spectrum of Tb _1.8 Eu _0.2 Mo ₃ O ₁₂ against BaSO ₄ as a white standard. FIG. 4 is the reflection spectrum of TbEuMo ₃ O ₁₂ for BaSO ₄ as a white standard. FIG. 5 is the reflection spectrum of Tb _1.8 Sm _0.2 Mo ₃ O ₁₂ for BaSO ₄ as a white standard.

FIG. 6 shows an excitation spectrum of Tb _1.999 Eu _0.001 Mo ₃ O ₁₂ (λ _em = 615 nm). FIG. 7 shows an excitation spectrum of Tb _1.8 Eu _0.2 Mo ₃ O ₁₂ (λ _em = 615 nm). FIG. 8 shows an excitation spectrum of TbEuMo ₃ O ₁₂ (λ _em = 615 nm). FIG. 9 shows an excitation spectrum of Tb _1.8 Sm _0.2 Mo ₃ O ₁₂ (λ _em = 600 nm). FIG. 10 shows an emission spectrum of Tb _1.999 Eu _0.001 Mo ₃ O ₁₂ (λ _ex = 487.0 nm). FIG. 11 shows an emission spectrum of Tb _1.8 Eu _0.2 Mo ₃ O ₁₂ (λ _ex = 487.0 nm). FIG. 12 shows an emission spectrum of TbEuMo ₃ O ₁₂ (λ _ex = 487.0 nm). FIG. 13 shows an emission spectrum of Tb _1.8 Sm _0.2 Mo ₃ O ₁₂ (λ _ex = 487.0 nm).

FIG. 14 is a portion from the CIE 1931 color scheme with Tb _2−x Eu _x Mo ₃ O ₁₂ color point. FIG. 15 is a lattice constant of a mixed crystal series of orthorhombic Tb _2-x Eu _x Mo ₃ O ₁₂ . FIG. 16 shows the LED spectrum of the pc-LED described in Example f).

Claims (15)

Formula I
_{(Tb 2) x (Mo 1} -b W b) y O 3x + 3y: Ln I
In which Ln represents Sm ³⁺ or Eu ³⁺ ;
x represents 1, 2 or 3;
1 ≦ y ≦ 8; and 0 ≦ b <1.
A compound represented by Formula Ia
_{(Tb 2-a Ln a)} x (Mo 1-b W b) y O 3x + 3y Ia
Wherein Ln, x, y and b have one of the meanings given in claim 1 and 0.1 ≦ a ≦ 1.
2. The compound of claim 1 selected from.   3. Compounds according to claim 1 or 2, characterized in that they are in phase pure form.   The compound according to claim 1, wherein 0.2 ≦ a ≦ 1.   The compound according to claim 1, wherein 0.4 ≦ a ≦ 1. 6. A compound according to any one of claims 1 to 5, wherein Ln is equal to Sm3 ⁺ .   7. A compound according to any one of claims 1 to 6, wherein x is equal to 1.   8. A compound according to any one of claims 1 to 7, wherein y is equal to 3.   9. A compound according to any one of claims 1 to 8, wherein b is equal to 0.   10. A process for producing a compound according to any one of claims 1 to 9, wherein in step a) a nitride and an oxide or europium or samarium source, a molybdenum source and a terbium source, and optionally a tungsten source. Said process, characterized in that suitable starting materials selected from the corresponding reactive forms are mixed and in step b) the mixture is thermally treated.   Use of a compound according to any one of claims 1 to 9 for partial or complete conversion of blue or near UV emission to longer wavelength visible light.   A luminescence conversion material comprising the compound according to any one of claims 1 to 9 and one or more further conversion phosphors.   A light source comprising at least one primary light source, the light source comprising at least one compound according to any one of claims 1 to 9 or a luminescence conversion material according to claim 12. .   14. Illumination unit, in particular for the backside illumination of a display device, characterized in that it comprises at least one light source according to claim 13.   15. A display device with back illumination, in particular a liquid crystal display device (LC display), characterized in that it comprises at least one lighting unit according to claim 14.